In case you've been biking to work every day and haven't seen a gas pump, you should know that prices are through the roof. That means many Americans are going to stick close to home this summer, trading a week at the shore for a trip to a relatively lower-cost national park.

Parks like Acadia, Yellowstone, Yosemite and the Great Smokies, which are already car-clogged, could get even more packed. So it might be better to head to the lower-profile parks, where crowds are rare but there's still enough to do to give the family a proper vacation.

What kid doesn't fantasize about being marooned on an island? Certainly anybody who's read Robert Louis Stevenson (or, more likely, watched "Survivor") has dreamed of life as a castaway. At Isle Royale National Park, that fantasy can dutifully be played out.

Once you step off the ferry, America may seem far, far away. Cars and bikes are banned on the paper clip-shaped bit of Michigan in Lake Superior and only 18,000 people visit a year. As a result, it's easy to feel like your family has the 45-mile-long stretch of wilderness to itself.

Set out on any of the 165 miles of hiking trails. Some lead to views of lighthouses -- there are four ringing the island -- while others, snake through velvety pine forests or brush by the ruins of 19th-century copper mines. The 1,074-foot Mount Franklin provides gauzy views of Canada and perhaps you'll come across some of the 450 moose that call Isle Royale home (or a few of the 30 gray wolves that occasionally make meals of them).

It costs just $4 a day to use the island, so camping is essentially free. But families may prefer renting a cottage -- $300 a night for four people during the peak summer season -- in Rock Harbor, which functions as the island's "town." Each comes with a built-in kitchenette, in case you want to go budget and cook your own grub.

Some places on Isle Royale are only reachable by water. You can travel by water taxi or rent a 14-foot aluminum boat with outboard motor to explore coves like Tobin Harbor, though the water might be too cold for a dip.

Still, that Great Lakes water is crystal clear, as evident from the six-hour ride there from the town of Houghton and the faster one, from Copper Harbor, which takes three. (Sea planes are another option from from Houghton). Although round-trip boat tickets can cost between $80 to $120, (depending on time of year) that may be a small price to pay for channeling your inner pirate.

If Isle Royale sits on top of the country, Big Bend National Park is squarely at the bottom, on the Mexican border in western Texas.

Big Bend's high desert landscape, graced with deep canyons and soaring peaks, doesn't get much rain (as little as seven inches a year). It also doesn't see too many visitors (about 400,000), since it's remote. The closest real city, Midland, is three hours away.

Yet kids who stay patient during the long journey find plenty waiting for them when they get there and, as parents will surely appreciate, all for just $15 per car per week.

Encompassing 800,000 acres where the Rio Grande River takes a jog to the north, Big Bend offers a dazzling array of wildlife with mountain lions, bears, lizards, bobcats and even those speedy roadrunners.